John Eells wrote:
Previously, I wrote:
(* Let's leave SYMBOLICRELATE out of it for now, until we all understand
the basics. Likewise, we can work our way up to what happens before
Catalog processes aliases and PATHENTRY entries for VSAM data seats, if
necessary.)
So now, let's look at what happens before Catalog is completely
initialized. During Catalog address space (aka "CAS") initialization,
the alias table (called the MLA table) is built. Before it's built, all
searches are oriented to the master catalog. After it's built, they are
oriented depending on whether there is an alias entry for the HLQ or
HLQs represented in each MLA table entry. (This is a logical view, not
necessarily how the code works in detail.)
The implication of this is that you can have *both*:
- One or more data set entries in the master catalog with a particular HLQ.
- An ALIAS entry for that same HLQ. (If you are using MLA, of course,
this can be more than one qualifier.)
Then, before the MLA table is built, the data set entries will be used
to find the data sets, but after it's built, the alias entry will be
used to reorient the search to the user cataog, and the data set entries
in the master catalog will be ignored.
While I am sure this can be construed to be "handy" to some, it is
pretty much guaranteed to confuse those who follow later, so I can't
really recommend that anyone actually do this. So I'll leave the order
in which such entries must be defined as an "Exercise to the Astute Reader."
(Still up...if I get to it...SYMBOLICRELATE and catalog orientation.)
--
John Eells
IBM Poughkeepsie
[email protected]
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